Sound transmission



4, 1931- w. B. JONES SOUND TRANSMISSION Filed Dec. 5, 1928 N'IPLIFIEQ Jonas Patented Aug. 4, 1931 UNITED STATES W. BARTLETT JONES, OF CHICAGO, ILIJI'OIS SOUND rmsinssxou Application filed December 5, 1928. Serial No. 828,886.

The present invention relates generally to sound transmission and reception, and in particular to apparatus such as stethoscopes and the like, far example the ear pieces and tube '6 connections used with dictating machines, or those employed in other phonographic reproduction. a

The present invention has resulted from a study of certain peculiarities in the sense of 1-; hearing, regarding the reception of sounds by the ears, having particular reference to the first reception by one ear and to a subsequent reception of the same sound by the other ear.

It is well known that sound is im roved in quality by the reception of reflecte portions of the sound, such as those which may reach the car from the walls of an auditorium. It is also known that when the reflected wave is 93 more than eighty feet behind the primary wave, the two do not merge into one sound but create an echo. Thisis the maximum limit for lagging waves. It is also known that when one ear hears a sound before the other car, and the time interval between receptions by the two cars is less than the so called binaural limit, the sound appears at some definite angle to the listener; and that if both ears hear the same sound at the same 39 time, the sound appears to come from a direction directly ahead or behind the listener.

I have noted that after sound is heard in one ear and when the other ear receives the same sound after an interval greater than the binaural limit, the sound reception in no way changes the perceived direction of the sound, but it does markedly change the character and quality of the sound. To illustrate:

A sound is conveyed, say by rubber tubing, A to the ear R. If the ear L receives the same out afiecting the ability of the sense of hearing to perceive direction by measuring the time interval between the two receptions of the primary sound. I

In Stethoscopes, and in phonographic receiving apparatus which carry, sound to the ears, it has long been the practice to conve the sound in one path, and then to split it into two paths, usually of equal length for presentation to the two ears. The sounds 00 thus heard are not the most natural sounds that can be obtained from a single tube. In such apparatus the present invention aims to divide and distribute the sound from a single source so that it may be received by the two ears with a more natural efiect.

Because of the more general use of dictating machines the invention will be specifically described with reference to devices and practices in this field. In this use of such 7 devices typists are obliged. to sit for long periods of time, typing words received by them at ear pieces from a phonograph record of the dictation. The more unnatural the sounds heard, the more strain there is on the operator. Furthermore, the listeners hearing may be defective, and there is now no provision for adjustments of the device to 'suit the hearing characteristics of the listener.

I have found that by several simple changes in the devices now in use, a greatly improved reception can be obtained. I believe I have discovered a principle which can be applied in a variety of fields in sound reception and transmission, as will appear more fully hereinafter from the description of the various devices illustrated in the accompanying drawings, in which:

Fig. 1 illustrates ear-pieces and connections for a dictating machine typist.

Figs. 2, 3, 4 and 5 are modifications of similar apparatus. r

Fig. 6 is a view showing a set of headphones modified acoustically for improved as reception.

Fig. 7 represents a set of head-phones with electrical mechanism to improve the acoustical presentation of sound.

Fig. 8 represents a set of head phones with we combined acoustic and electric mechanism to improve the presentation.

Fig. 9 represents an adaptation of the principle to the recording of dictation.

I will first describe the apparatus shown in Fig. 2. Numeral 10 represents a single source of sound, such as the diaphragm on a stethoscope, a dictation phonograph, or a telephone receiver. The reproduced sound is conveyed by a tube 11 and split into two branches 12 and 13, which in turn are respectively split into two branches 14-15 and 1617. Branches 15 and 17 are made to cross each other, and are much longer than the companion branches 16 and 14. Branches 14 and 17 are combined by a Y-connector 18, and branches 15 and 16 are combined by a Y-connector 19. Ear pieces 20 and 21 present the recombined sounds to the ears.

It will be observed that paths 1112 141820 and 111316-19-21 are illustrated as equal in len th and are shorter than the other pair 0 equal length paths 11121519-21 and l1-13-17-18- 20. Therefore, each ear receives the same combination of sounds at the same time. But each combination has a leading or primary component and a lagging or secondary component. Should the tubes be plnched at the region 22, so as to cut off both crossing connections, the secondary components become eliminated and the primary wave of the apparatus 10 is heard in each ear. The character of the sound will be rendered inferior by the pinching described, and improved hearing will be established upon release of the tubes from the pinched condition. Each ear then receives the primary components at the same time, and later, each ear hears the same sound after an interval corresponding to the added length of path. The improve hearing for each ear is due to the combined first hearing in that ear and the second hearing of the other ear.

I have found that when the delayed sound lags a distance greater than the binaural limit, the time interval between the primary waves can be varied within the binaural limit, to indicate direction or angularity of source, or to move the apparent source angularly to the listener. This permits adjustment of the apparent source of sound to abnormalities in hearing. Even for normal persons it permits sound to be placed more to the side where other disturbing noises may be heard, so as to overcome such disturbance.

Fig. 1 shows how this can be done. A headgear 23 is connected as inFig. 2 above described. The source 24 (corresponding in character to source 10 in Fig. 2) is connected by a tube 25 which is split into two paths 26 and 27, each branch path containing telescopic tubular connectors 28 for varying the lengths of the paths 26 and 27. When path 27 is elongated into the length indicated in dotted line path, ear-piece 30 receives the primary wave before ear-piece 31. The lagging secondary wave in ear-piece 31, which is the mate for the primary wave in earpiece 30, remains unchanged, and the lagging secondary wave in ear-piece 30 is additionally delayed equally with its companion primary wave in ear-piece 31.

In Fig. 1 four paths are created which are designated A, B, C, and D. Paths A and B are the shortest paths to the two ears and through a lengthening of path 27 to the length 29 they may vary within the binaural limit to favor one ear earlier than the other ear. The paths C and D are respectively longer than the paths B and A by a length greater than the binaural limit, so that after one ear hears sound through A (or B) the other ear hears the same sound through D (or C) after an interval too late to determine a directional effect.

In Fig. 3 the crossing connection is eliminated and each of the two branches 32 and 33 divide into a short branch 34 and a longer branch 35, which are recombined at 36. The net effect is the same, but I have observed that better results are obtained in the connections of Figs. 1 and 2. In explanation of this observation I submit that the companion primary and secondary effects heard by the two ears should be as nearly identical as possible. In Fig. 2 the secondary Wave in tube 16 is taken ofi from the companion primary wave in tube-path 12-14. In Fig. 3 the paths of the companion waves have a less length in common and are independent over a greater length, permitting move variation in transmission to result by internal reflections from the tube walls.

In Fig. 4 a common source is attached to a tube 41, which is split into two branches 42 and 43, which are respectively split into two branches 4445 and 4647. Branches 43-46 and 4347 are made longer than branches 4244 and -42. A combination of long and short branches is made for each ear at 48 and 49.

Fig. 5 is an improved arrangement in which a head-gear 50 having ear-pieces 51 and 52 is employed as a carrying bridge for acoustic tubes 53 and 54. Each ear-piece receives the primary wave from the tube 55 or 56, each of which is tapped by one of the tubes 53 and 54 that leads to the opposite ear-piece.

F 1g. 6 shows a pair of head-phones and 61 into the backs of which acoustic tubes 62 and 63 are connected for carrying sound from one phone to the ear at the opposite phone. An ear-piece 64 is provided over each phone to receive the acoustic tube.

Fig. 7 illustrates how to accomplish the purposes of the invention electrically. A pair of head-phones is connected in circuit 71 with two transformer or induction coils 72 ahd 73 coupled respectively to coils 7 4 and 75, interconnected by an amplifier 76, if one is necessar a delay circuit 77, and an amplifier 78 (if necessary). The len th of the delay circuit and the use of amplifiers may be proportioned to secure the desired volume in the l ging waves in each of the earhones. In t is circuit of Fig. 7 the delaye sound wave again becomes operative upon the delay circuit to provide a further delay, causing continued re etition of the sound. It is to be understood that the delay 'eriod and the intensity of the first delaye sound should be controlled to prevent building up of the delayed waves to overcome the primary wave, and to permit the delayed waves to die out. The intensity of the delayed wave should therefore be made less than the primary wave, and no delayed wave of about an eighty-foot lag should be heard. It should also be understood that the multiplication of the delayed waves can be avoided by introducing an additional circuit, according to the principles involved in Fig. 8.

p In Fig. 8 an acoustic path is employed as delaying means. A line 80 carrying current corresponding to sound has two induction means 81 and 82 in its circuit. These are respectively coupled to a head-phone circuit and a delaying circuit throu h suitable coupling, regulating or ampli ying apparatus 83 and 84. The head-phone circuit 85 has induction means 86 therein and head-phones 87. The delay circuit 88 contains a sound producer 89 operating over an acoustic path 90 into a pick-up device such as a telep one transmitter 91 in a local circuit 92 coupled to the induction means 86 of circuit 85.

The devices of Figs. 1 to 8 are directed to the receiving end, or the transmission of sound or records of sound to the ears of a listener for improved reception. With reference tothe dictation phonograph field it is to be understood that the devices shown and herein described are particularly adapted to effected prior to making the record, so that the record contains the same type of compound wave. In Fig. 9 I show means for doing this. The device herein shown compounds the wave in an acoustic path by bypassing one portion into a longer or delay- 1n channel, so that when the two are 'reunited, the original and the by-passed portion are compounded in an out-of-phase relation. In Fig. 9 a recordis indicated at 94, a cutting stylus at 95, and the stylus box at 96. The main speaking tube 97 has a by-pass 98 arranged to divert about half the sound ener into the longer path at the pgant 99, an to reunite the two portions at The record 94 may be used with the usual Y-type of head-"ear connection now in use to obtain the desired effects of this invention, or it may be used with the improved apparatus to improve the hearing to a still greater degree by the additional delayed waves that are impressed on the ear.

From the foregoing it will be apparent to those skilled in the art that a number of different embodiments-giro ossible as contemplated by the scope o "the appended claims. s

I claim:

1. The method of transmitting an original sound to human ears which comprises, converting a wave form corresponding to said sound into two similar portions, delaying one ortion relative to the other portion, recomining the out-of-phase wave forms, converting t e resulting wave forminto two portions, and presenting the divided portions as sound separately to each ear.

2. The method of transmitting an original sound to human ears which comprises presenting said sound separately to each ear at intervals less than the binaural limit, and subsequently presenting the said sound to each ear. I

3. The method of transmitting sound to human ears which comprises presenting primary sound to each ear, delaying said sound to form secondary sound, and subsequently presenting the secondary sound to each ear.

4. The method of transmitting sound to human ears which comprises presenting sound to one ear, and conducting the same sound to the other ear overyan acoustic path which is sufliciently long to delay its arrival for a period not less than the binaural time limit. 7

5. The method of transmitting sound to human ears which comprises conducting sound through an acousticpath to one ear and conducting the same sound to the other ear through an acoustic path which is longer by an amount not less than the binaural time limit.

. 6. The method of transmitting sound to human ears which comprises conducting sound through separate acoustic paths to each ear at intervals less than the binaural time limit, and conducting the same sound to each ear over an acoustic path which for one ear is longer than the path to the other ear by an amount not less than the binaural limit.

7. The method of transmitting sound to human ears which comprises conducting sound through separate acoustic paths to each ear at intervals less than the binaural limit, and conducting the same sounds to each car over an acoustic path which for any one ear is longer than the path to the other ear by an amount not less than the binaural limit, and, controlling the time of arrival over the shorter paths at the respective ears, in accordance with the particular characteristic of the individual.

8. Apparatus for hearing sound which comprises an acoustic ear piece for each ear, two means of unequal length forming two acoustic paths to each ear piece, two Y-means havin each three acoustic branch paths, said Four-path formin means being connected in any way to our branches of the Y-means leaving one unconnected branch on each Y, and means for delivering the same sounds to each remaining Y-branch.

9. Apparatus for hearing sound which comprises an acoustic ear piece for each ear, two means of unequal len th forming two acoustic paths to each ear piece, two Y-means having each three acoustic paths, said four means being connected in any way to four branches of the Y-means leaving one branch on each Y-means unconnected, two means forming acoustic paths of equal lengths, a third acoustic path Y-means connecting said equal length means, the remaining branch of the third Y being adapted to receive a single sound.

10. Apparatus for bearing sound which comprises in combination, means formin an acoustic path for sound, said means divi ing the path into two acoustic branches,'means dividing each branch ath into'two subbranches, the total len s of two paths from the first division varying less than the binaural limit, the shorter being A and the longer B, the length of the remaining paths from the first division being such that one of them C is longer than A by an amount not p less than the binaural limit, and the other D being similarly longer than ea-r pieces for each ear, A and C being connected to one ear piece and B and D to another ear piece.

11. The method of picking up sound for making a record or a transmissible eflect thereof which comprises pickin up a primary wave of said sound in a pic -up device, by-passing a portion of said primary wave in an acoustic path, and returning said bypassed sound to the pick-up device after expiration of the binaural time limit.

In tesimony whereof, I have hereunto ailixed .my signature.

W. BARTLETT JONES. 

